Date: Wed, 24 Jun 2009 14:55:07 +0200 From: =?iso-8859-1?Q?Eirik_=D8verby?= <ltning@anduin.net> To: "Tom Haapanen" <tomh@motorsport.com> Cc: freebsd-jail@freebsd.org Subject: Re: Memory usage across multiple jails Message-ID: <A80E3184-F365-4D6C-86DD-1209B61D4D82@anduin.net> In-Reply-To: <0c9201c9f4c9$ec3d1640$c4b742c0$@com> References: <0c1201c9f43e$166c8450$43458cf0$@com> <4A41461D.4000009@modulus.org> <0c9201c9f4c9$ec3d1640$c4b742c0$@com>
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On 24. juni 2009, at 14.47, Tom Haapanen wrote: > Andrew Snow wrote: >> * the jails share disk cache >> * jails don't have any reserved memory so any unused memory returns >> to >> the free pool of the kernel, available for disk cache >> * there is a single kernel shared across all jails >> * userland code can also be shared across jails *if* you run the code >> from the same set of on-disk binaries (which is not the way most >> people >> set up jails) >> * since there is only a single kernel all network and disk I/O from >> the >> jails goes at the same speed as the host > > Thanks, Andrew (and Michael) -- that sounds very good. It certainly > looks > like I should be able to achieve some resource efficiencies this way > vs > running multiple physical servers. We are running a number of high-volume services on jails, and have been doing so since the days of FreeBSD 4.x. The hardware utilization has always been good, and has gotten significantly better with each of the releases of FreeBSD 6.x and, now, 7.x. > I'm also further educated about VMware ... though that's less > important for > me at the moment as I would really prefer to run the host on FreeBSD > as well > (and I suspect those required guest drivers aren't available for > FreeBSD, > either). No VMware running on top of another OS is going to perform anywhere near satisfactory. You'll need ESX or something else running on the bare iron (XEN?) to get anywhere near what jails (FreeBSD), vservers (Linux), zones (Solaris) etc. will give you. Of course it could be argued that the levels of separation and resource control will be different (sometimes better) with emulators, but in no other way than the intimacy of the host<->jail coupling on FreeBSD give you significant benefits too. For example, (security) auditing of jails can be done on the host, and the host can be considered a separate machine from the jails for most intents and purposes. For compliance (PCI-DSS) it is quite perfect. /Eirik
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